This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The objective of this study is to define the consequences of naturally-occurring age-related hearing deficits on the structure and function of the central auditory system. These results will be used to develop more effective hearing-assist devices (hearing aids) for the 70 million Americans that currently suffer from age-related hearing deficits.